The Water-soluble Vitamins (Vitamins and C).— As has been seen from the foregoing, the water-soluble vitamin of McCollum and Davis was found to be effective in two different ways, the cure or prevention of polyneuritis in pigeons (and beri beri in man) and the maintenance of growth and well being in rats. Both of these effects were produced by a long list of food stuffs, the most efficacious being yeast, egg yolk, fish roe and the embryos of seeds.
It was at first thought that only one vitamin was concerned in these effects (1916 McCollum and Kennedy) but further investi gation has gradually shown that in all these sources at least two vitamins are present, which can be distinguished both by their behaviour towards external factors (heat, etc.) and by the effect on the animal organism of their absence from the diet.
These are best termed vitamins and B2, but at the date of writing unanimity on this question has not been attained and they are sometimes termed vitamins F and G (Sherman).
Vitamin (the Antineuritic Vitamin).—To the vitamin which guards against and cures beriberi in man and polyneuritis in birds (1897 Eijkman) the name vitamin has been assigned. Although capable of withstanding the temperature of boiling water for one or two hours, it is readily inactivated when its solution is heated under pressure at '20°. C, at which temperature vitamin which invariably accompanies it in natural sources, is scarcely affected.
Preparations have now been obtained which are highly active in the prevention and cure of polyneuritis in birds, a daily dose of 0.5-0.05 milligram being sufficient to keep a pigeon in good health. It has, however, no effect in curing or preventing the specific effects of absence of vitamin (see below) and does not by itself produce growth and well being in rats, the simultaneous presence of both water-soluble vitamin and B2 being essential.
known to be of dietetic origin and to be curable by a proper diet.
Little is so far known about the relative amounts of vitamins and in those materials in which they occur together. Judged by their effect on human pellagra (Goldberg), milk, eggs, wheat germ and tomato juice all contain vitamin in smaller amount than lean meat, which is itself surpassed by yeast. Vegetables and fruits only contain very little and it is absent from oils and fats.
Vitamin C (the Antiscorbutic Vitamin).—The cure for scurvy was long recognised to be fresh food but quantitative experiments have shown that the vitamin occurs in very varying proportions in different food materials. Its richest sources are green leaves, especially of the cabbage tribe, the juice of citrus fruits (lemon, orange, and grape fruit), the tomato and certain roots such as the swede turnip. On the other hand meat and milk, the potato and many vegetables and fruits usually only contain the vitamin in comparatively small amount. It is absent from seeds but is produced on germination (1912, Fiirst). Different animals vary greatly in their requirements of this vitamin. Thus guinea pigs (250-300 g.) need oo-150 c.c. of milk or 1.5 c.c. of orange juice or 1.5 grams of fresh cabbage per day, whilst mon keys, ten tunes their weight, require exactly the same ration; rats on the other hand require extremely little and can exist for long periods without it.
Of all the known vitamins, the antiscorbutic is the most readily inactivated by oxidation. This process is comparatively slow at air temperature but becomes very rapid when the temperature is raised. As a result of this a large proportion of the anti scorbutic potency of food materials is lost when they are cooked or dried. In the process of canning there is less exposure to air and some canned articles e.g. tomatoes, are still potent. Inactiva tion by oxidation is greatest in alkaline and least in acid solutions.